Aniston, who wants a low-key ceremony at the Bel Air mansion she shares with Theroux, reportedly wants Alex, often called AJ, to serve as Theroux's best man.
Fortunately, her fiancé is on board.
"Justin feels that having AJ act as his best man at the wedding will give him an anchor in the family," a family insider said. "There's no doubt that AJ is quirky, but he's got a good heart and Jen does love him."
AJ is known as something of a punk and a free spirit, with a number of tattoos and a penchant for drifting between Alaska and Los Angeles in his van.
"AJ is exactly the kind of person that security would throw out of Jen's wedding," the source said. "Instead, he'll be front and center at the ceremony."
Aniston reportedly wants to keep the wedding, her second, small since she "hated" her wedding to Brad Pitt.
"It was too big and incredible stressful," the insider said. "This time she wants a small family affair and she wants to go the extra mile to let her father see that she is still happy at last. And she knows that including his son would make him happiest."
As to when that wedding will take place, we'll just have to wait and see.